Make your AR even more adaptable with the Magpul MBUS Back Up Front Sight. Magpul makes high quality injection molded parts and accessories, primarily for the AR15 rifle platform, right here in the USA. Polymer backup sights are popular for several reasons, including low weight, quiet operation, and durability. High quality polymer can take a certain amount of abuse without breaking, and still return to its original form, unlike metal, which may permanently deform, or even break.